Process for producing composite metals



Patented Apr. 22, 1 930 UNITED STATES PATENT OFFICE,

HENRY L. COLES, OF' HAMILTOLI, OHIO, ASSIGNOR TO GUARDIAN METALSCOMPANY, OF HAMILTON, OHIO, A CORPORATION OF DELAWARE PROCESS FOR.PRODUCING COMPOSITE MET ALS No Drawing. Original application filedNovember 22, 1927, Serial No. 234,957. Divided and this applicationfiled November 9, 1928.

This application is a division of my appli-- cation, Serial N 0.234,957, filed November 22, 1927, for composite metals and process forproducing the same. 5 This invention relates to an improved process forfabricating composite. metal plates and the like. In my applicationabove referred to, there has been described a process for fabricatingcomposite metal plates, and more particularly the improved productresulting from such process. In the present case, in order to secureintimatecontact between the metal of the core and of the sheath to' forma composite or compound metal plate, the core members are firstsubjected to a preliminary treatment.

In this treatment the metallic core is sandblasted or otherwisetreatedto remove surface matter such as oxidesand the like, after 2 which it issprayed with a concentrated solution of a nitrogenous material such asalkali nitrite, my preferred composition being sodium nitrite (NaNo Thefunction of the sodium nitrite is to improve the wetting qualities ofthe core metal and adapt it to be wetted by the molten sheathingmaterial or' metal such as copper or the like. Usually after spraying,heat is applied by a torch to dry the core, care being taken to restrictthe an amount of heat to that necessary for drying, without effectingany substantial decomposi tion of the sodium nitrite. The result of thistreatment is ametallic core intimately coated with a layer of the sodiumnitrite. When molten metal, such as copper, is cast in and around such acore member, it decomposes the sodium nitrite, liberating quantities ofgases such as nitrogen which serve to force out the air from the moldchamber and to 40 provide .substantially oxygen-free atmosphere therein.This freedom from oxygen prevents the formation of the noxious oxides ofcopper, and with these oxides absent, the unalloyed character .of ahighly refined sheath metal may be preserved.

A particular example of the im roved results to be procured by theapplication of the present process is in the casting of com;

pound metal bodies for use in the manufac- 'ture of burglar-proof safesand vaults, as

Serial No. 318,313.

exemplified in my present application, above noted, in which a metalliccore of drill-proof metal composition or alloy, of the types disclosedin my co-pending applications, Serial Nos. 730,194 and 86,034, (in whichthe compositions include preponderating amounts of tungsten with minoramounts of molybdenum, carbon or copper, or ferrous alloys having a highpercentage of chromium and mangenese) is formed into any desiredconfiguration, and intimately coated with a concentrated solution ofsodium nitrite. These sotreated' bodies are then placed in a mold, orthey may be preliminarily placed in a mold and the nitrite solutionapplied by spraying, after which a suitable sheathing metal such ascopper is poured into the mold. During the casting operation the moltenmetal is preferably poured as slowly as is consistent with results to beobtained. The

primary consideration is that the molten metal shall contact with thecore metal at such a rate of speed as will insure an adequate preheatinthereof without chilling the pour. This pre eating also serves todecompose the nitrite coating, setting free gaseous nitrogen and itsoxides, which, as has already been pointed out, sweep out the air fromabove the surface of the advancing metal.

The alkali molecules set free by the decomposition of the nitrite unitewith any siliceous impurities present, and form a freeflowing slagcoating over the surface of the pour, thereby adding an additionalprotective agent to co-actwith the gaseous blanket previously described.The thorough cleaning which the surface of the core metal undergoes, asa result of this treatment, greatly enhances the wetting capacity of themolten metal by assuring an absolutely clean metal to metal surface. Theadvancing metal flows into and through the interstitial spaces betweenthe slats of which the core is preferably formed, forming asubstantially contin uous sheath therearound; and being in intimatecontact therewith,the result is essentially a composite metal platecomprising a hard core of drill-resistant metal and an outer protectingsheath of ductile and comv solutionof the constituents of the severalalloys proceeds under optimum conditions, and the core and sheath arejoined in a substantial mono-metallic structure.

The processherein described is adapted for a wide variety ofmetallurgical purposes, and more particularly for the casting. ofnonferrous metals generally, which are readily oxidized in their moltencondition. The ease of decomposition of this material, sodium;

nitrite, is of particular i ortance in the present invention, as itafior s a ready means of providin a non-oxidizing atmosphere in castingmol and the like without involving the necessity of using gaseousnitrogen, or other non-oxidizing gases with the attendant trouble of theapparatus'required.

' By way of rsum it will be noted that by merel coating the'moldwalls'with a concentrate solution of sodium' nitrite, or any othersuitable compound, such as the other alkali nitrites, the molten metalin contact with the mold walls readily decomposes the alkali nitrites,-co ious volumes of nitrogen gas is set free an acts to sweep, or forceout. any air present from the mold chamber; In addition, the alkaliresidues set free by the liberation ofthe nitrogen component react withany siliceous material present to form a freeflowing slag which coversthe top of the advancing metal, thus co-operating with the non-oxldizinggaseous blanket to prevent any contact between the metal and the outsideair. Where core members of non-ferrous metal are used, the cores arepreviously coated with the concentrated nitrite solution, and due to thevigorous chemical action between the con stitutents of the nitritecompound and any non-metallic impurities which may be present on thesurface of the core under the influence of the molten metal, the coresurface is thoroughly cleansed and presented to the advancing metal, notonly in a condition wherein it is free from occluded oxygen and thelike, but also in which it is particularl adapted to combine or alloywith the sheet metal, where such alloying is possible.

Itwill' now be appreciated that there has been provided an improvedprocess for the 'productionof composite metal castingsythis processbeing characterized by the discovery that the presence of an alkalinitrite in the mold, or,applied to= a core member in a mold,

enables the ready preparation of diflicult castings without involvingany great expense in special machinery required forgaseous deoxidants oflike blanketing materials.

3. A- method of producing compound metallic plates, comprising coatingan apertured core member with sodium nitrite and casting a sheath ofmetal in and around the core.

4. A method of producing compound metallic structures comprising coatingan apertured core member with sodium nitrite, casting a sheath of metalaround the core under determined conditions of temperature and rate ofpour, whereby to assure optimum conditlons' of reaction. 1

5. A method of producing burglar-proof safes, comprising forming adrill-proof core member, spraying the core with sodium nitrite, andcasting a heat-conductive metal in and around the core.

-6. A method of producing burglar-proof vault doors, comprising formmg adrillproof core member, spraying the core with an alkali nitrite, andcasting a sheath of heatconductive metal in and around the core.

7. A method of producing compound metallic plates, comprising casting asheath of metal around a metal core member in' the presence'of nitrogenliberated in situ.

8. A method of producing compound metallic plates, comprising casting asheath of metal around a metal core member in the presence of nascentnitro en,

9. In the production of metallic compound plates having an inner coremember and an external sheath cast therearound, the improvement whichcomprises simultaneously cleansing the surface of the core member andforming a non-oxidizing protective atmos-' phere about the said core byreacting the molten sheath metal with a compound adaptgd to liberatenitrogen gas and an alkali resi- 10. In the production of compound methemold with a nitrogenous compound adapted .to liberate nitrogen gas and aslag-forming residue when strongly heated, and flowing a molten sheathof metal into said mold and around said core, whereby to form anatmosphere of nitrogen gas in the mold cham- 1 her and a free-flowingslag coating on the said flowing molten metal.

This specification signed this 8th day of November, 1928.

HENRY L. COLES.

